Elastomeric compositions are used in a wide variety of applications, including tire components such as treads and sidewalls, hoses, belts, footwear components, and vibration isolation devices. The selection of ingredients for the commercial formulation of an elastomeric composition depends upon the balance of properties desired, the application, and the application's end use.
For example, in the tire industry the balance between processing properties of the green (uncured) composition in the tire plant and in-service performance of the cured rubber tire composite is of particular importance. The ability to improve the endurance of tires used in a wide variety of conditions, such as is required for agricultural tires, aircraft tires, earthmover tires, heavy-duty truck tires, mining tires, motorcycle tires, medium truck tires, and passenger car tires, while maintaining ease of processability of the uncured elastomeric composition is also of significant importance. Additionally, the goals of improving air impermeability properties, flex fatigue properties, and the adhesion of the elastomeric composition to adjoining tire components without affecting the processability of the uncured elastomeric composition or while maintaining or improving the physical property performance of the cured elastomeric composition still remain.
Conventionally, various processing oils, such as naphthenic, paraffinic, and aromatic oils, have been added to most tire components to aid compound processing. Aromatic oil has been preferred due to its processing effectiveness and beneficial secondary properties, e.g., adhesion. However, these processing oils, particularly aromatic oils containing distilled aromatic extracts, are being replaced due to health, safety, and environmental concerns. For example, European Union Directive 2005/69/EC is requiring the reduction of polycyclic aromatic hydrocarbons (“PAH”) in passenger car tires, light and heavy truck tires, agricultural tires, and motorcycle tires by Jan. 1, 2010. Thus, rubber compounders will need to replace current aromatic oils in oil-extended (“OE”) rubbers with alternative oils or look for other alternative processing aids.
Current industry PAH oil replacement options, such as treated distillate aromatic extracts (“TDAE”) and mild extract solvates (“MES”), are limited in supply and have shown deficiencies such as reduced dynamic properties, reduced tire wet traction performance, reduced tear strength, and reduced tire durability (e.g., tire component-to-component adhesion may be less with TDAE and MES than with conventional aromatic oils). Therefore, a need exists for a replacement for processing oils, such as PAHs, in tire and tire tread compounds which will maintain beneficial compounding properties and without adversely impacting tire performance.
Conventional oil processing aids have been used in many tire components: tread compounds often contain polybutadiene rubber (“BR”), oil-extended polybutadiene rubber (“OE-BR”), styrene-butadiene rubber (“SBR”), oil-extended styrene-butadiene rubber (“OE-SBR”), isoprene-butadiene rubber (“IBR”), and styrene-isoprene-butadiene rubber (“SIBR”); sidewall and ply coats can contain butyl rubber and SBR and may use free aromatic oils as processing aids; internal components, such as the steel belt skim coat, gum strips, cushions, barriers, bases, and wedges, contain predominantly natural rubber and aromatic oils. Generally, the raw ingredients and materials used in tire compounding impact all tire performance variables, thus, any alternative to conventional processing oils must be compatible with the rubbers, not interfere with cure, be easily dispersed in all tire compounds, be cost effective, and not adversely impact tire performance.
As many tires are compounded and engineered for particular performance characteristics, it is desirable that any replacement for traditional aromatic oils maintains tire performance characteristics, such as rolling resistance, traction, and wear performance. There is a need for a replacement for aromatic oils in tire and tire tread compounds; in particular, there is a need for an aromatic oil replacement which allows for beneficial compound processability and does not adversely impact tire performance.